leaper, leapling
According to a Detroit Free Press article, "Leap year babies hop through hoops of joy, pain of novelty birthday" (doesn't "Hoops of Joy" sound like it should be part of the same series as "Abs of Steel" and "Blades of Glory"?), a baby born on Leap Day is a "leapling," and an adult born on Leap Day (that is, a former leapling who's now grown up) is a "leaper."